This invention relates generally to the technology of energy and liquid recycling and more particularly to an improved compressor apparatus for use in such technology. Such an improved compressor has great potential for use in vapor compression distillation and other applications in which low levels of vibration and steady flow output and constant pressure are desirable.
Vapor compression distillation is well known and understood in the broader field of distillation of liquids. In a vapor compression system, a liquid supply is at least partially evaporated. The vapor extracted is then adiabatically compressed thus elevating the temperature at which the vapor will recondense to some value higher than its original evaporative temperature. When the vapor recondenses it returns all of the latent heat that originally went into evaporating it back to the system The only energy placed into the system which is not recovered is the energy required to compress the vapor.
Vapor compression distillers generally make use of centrifugal compression, due to the simplicity, cost-effectiveness, and reasonable efficiency of the centrifugal process. However, as the distiller is scaled downward, centrifugal compression becomes more problematic. Efficiency falls off rapidly below 25 gallons of distillate per hour. As the output of the distiller decreases so too does the efficiency of the centrifugal compressor.
Compressors operating on the principle of reciprocation are more efficient in smaller sizes but generally are not suitable for vapor compression systems. Some of the problems associated with reciprocation are: 1) a piston-based compressor is more mechanically complicated and generally requires lubrication of the piston rings within the cylinder; 2) a piston-based compressor exhibits more severe wear characteristics; and 3) a piston-base compressor introduces pressure pulses due to the action of the piston.
There is no theoretical lower output limit to a vapor compression distillation unit. However, the practical problems associated with low output vapor compression which limit its feasibility are due to: 1) inefficiencies in heat transfer between the vapor and the incoming liquid; and 2) the compressor design. Low output vapor compression distillation is desirable for small incoming liquid streams such as commonly occur in residential waste collection systems. By distilling the water from a household waste stream and recycling it for use in watering the lawn, the garden or even as potable water great savings in waste management will be gained. Other uses certainly abound for systems operating at volumes less than 25 gallons per hour.